KDE is one of the major desktops available for Linux, the desktop means in this case the graphical interface that user sees in front of him when he is using his openSUSE system. KDE went through major changes from the "old" KDE 3.5 series to the new KDE4 series, to a point that the new KDE is a complete re-design of the desktop metaphor. KDE has always been my choice on desktop and because openSUSE does great job 'releasing' KDE it has only deepened my admiration for the openSUSE project. KDE.org has a nice visual guide to KDE4, check it out!
YaST is no doubt one of the single most greatest aspect of openSUSE Linux distribution. People that have not used it seem to think that it is yet another package manager (if that was the case it would be called YaPM). Truth is that YaST is so much more than simple software installation tool, it is everything that is missing from most other Linux distributions and that is a centralized system administration tool that makes configuring your system easy. Want to partition your drives? Simple, use YaST. Want to setup your monitor to correct resolution? Again thats simple just launch YaST. Want configure file serving or other server functionality? YES, use YaST!
In video below I'll shortly present the two aspects I like most about openSUSE, as described above they are: great KDE desktop implementation and YaST. By KDE implementation I am not saying that openSUSE devs did all the work, but they compile a great release with fixes and polish to the KDE code.
Notice, the above video should load, by default, in HD mode. So just ignore the recommendation on the video to "turn on the HD resolution".